Tuesday 17 July 2012

Truing and bearing the cones-equences

I rode around on my new front wheel for a while. Then one day I was sitting in my office at work, when I noticed that one of my spokes was loose enough to rattle with my fingers.

I know enough to know that's not good. So I thought I'd better do something about it. That meant buying a spoke wrench... and while I as at it I though I might get some cone wrenches as well.



I tightened up the loose spoke, but then I was in dangerous territory. Now I had the tools to do some proper damage. Truing wheels and adjusting wheel bearings seemed like serious bicycle mechanicery. Sheldon calls truing the "trickiest" job in bicycle maintenance, "a person who tries to 'touch up' a slightly out-of true wheel without proper knowledge could turn an imperfection into a disaster".

I talked to my hardcore Canadian cycling buddy about it. She agreed it was a tricky business. She told me about her ex boyfriend who spent hours doing cones and tweaking his spokes (she mimed him inhaling thoughtfully and stroking his chin). But when she tried it, she thought she'd done a good job, only to have her wheel EXPLODE when she bumped down off a gutter!

There are a few points to ponder in that story:
  • hardcore cycling buddys can be girls.
  • "cones" may have more that one meaning, but more about hub adjustments in a moment.
  • why no nipple jokes?
  • why would a badly trued wheel EXPLODE!?
There are four things you can adjust with a spoke wrench, vertical true, lateral true, dishing and spoke tension. To make things complicated, every adjustment you make with the wrench changes all four at once. So truing has to be a process of many slight adjustments and readjustments, with much careful reflection and deep consideration of each move ... just the sort of thing that people who fiddle with bicycles love. With a mug of tea for me!

Sheldon Brown says the best way to learn truing is to start by building wheels from scratch, better than trying to repair dented and damaged rims, but I've started by just making small adjustments to some new wheels that have loosened up a bit after they've first been ridden. I have no truing stand, so I put the wheel on the upside down bike, with the tyre and tube off. I use the brake pads to check lateral true and hold a straight edge against the frame to check vertical true. I haven't really worried too much about dishing with the small adjustments I'm making. Perhaps I'll need to get a dishing stick next. Sheldon gives highly detailed instructions of what to do. Just remember the saying "better is the enemy of good", which I hear from an orthopedic surgeon, and know when to stop.



I suspect my friend's EXPLODING wheel was due to a problem with spoke tension. There is such a thing as a tensiometer which measures spoke tension, but I've just tuned them all to around F# above middle C (John Allen has a nice table of spoke lengths,  and musical pitches for butted and unbutted spokes).

After that, servicing and adjusting cone and cup hubs was easy. Apart from the worry of dropping ball bearings all over the floor, it essentially involves tightening small nuts against each other on a treaded axel with some funky little skinny wrenches. With small adjustments I tighten the cones just enough to eliminate any play from side to side. Sheldon says most bicycle hubs are adjusted too tight. Quick release clamps compress the axel and tighten the bearing a tiny bit so you can leave a tiny bit of play and check that it is gone when the wheel is on the bike.






So I trued and adjusted my wheels. What was the worst that could happen? Catastrophic failure at high speed, throwing me into on-coming traffic, a severe head injury and the rest of my life in a coma?


No. But I have gotten a little addicted to fiddling with my wheels. It's great to pick up your bike, give the wheel a flick and watch it spin 4 EVA. But with the cones adjusted so finely, I have to keep checking that they haven't loosened off and started rattling. I now realise that the hours I spent as a youth adjusting the cantilever brakes on my hard ridden mountain bike, would have been better used carefully straightening out my lumpy rims. And I've found that riding along looking down at a freshly trued, radially spoked, front wheel, rotating but almost looking like it's not moving, is quite mesmerising. I have to remind myself to look up.... another way to end up in on-comming traffic.